Ministers will today propose £200 one-off payments to families that are failing to take up services offered by the Sure Start scheme, such as health jabs, help with children's reading and parenting.

The payments will be announced as part of a speech by the prime minister, Gordon Brown, on social mobility, to be delivered at the Specialist Schools and Academies Trust, which manages the government's specialist schools programme.

The payment is aimed at what the government describes as hard-to-reach families that are seen as being most in need of help from Sure Start in raising their families, but do not come forward to use the services.

It will be available only to parents of children under five, and is likely to be dismissed by the Tories as a bribe or a gimmick. The funding for the proposals will be drawn from £125m set aside in the budget over the next three years to address child poverty.

The scheme will be piloted in some of Britain's lowest-income areas and will initially cost £13m.

In his speech Brown will say: "Social mobility starts with the parents wanting their children to do better than they did themselves.

"But it cannot be achieved without people themselves adopting the work ethic, the learning ethic, and aiming high, so it also depends on the government giving people the capacity to participate fully in shaping their future."

He will claim that social mobility stalled in the 1970s and 1980s, saying: "At a time when many of their fathers were being hit by unemployment, many of their generation, that some have called Thatcher's children - the lost generation - were sadly denied their chance to progress."